Hemophilia is an inherited disease which has been known for centuries but it is only within the last three decades that it has been possible to differentiate between the various forms; hemophilia A, hemophilia B and hemophilia C. Hemophilia A is the most frequent and affects only males in frequency of one or two individuals per 10,000 males. The disease is caused by strongly decreased level or absence of biologically active coagulation factor VIII or as it also has been called the antihemophilic factor. Factor VIII is a protein normally present in plasma. The clinical manifestation of hemophilia A is a strong bleeding tendency and before treatment with Factor VIII concentrates was introduced the mean age of death of hemophiliacs was less than 20 years. Concentrates of Factor VIII obtained from plasma has been available for treatment of hemophilia A for about two decades. This has improved the situation for hemophilia patients considerably and given most of them possibility to live a normal life. However, there are certain problems with the concentrates and their use. The concentrates presently available are rather impure having a specific activity of less than 2 units Factor VIII/mg protein and containing &lt;1% of Factor VIII protein. Further they are fairly expensive because the starting material, plasma, is expensive and the yields in the purification processes used are low with the low purity products. There is also the risk for transmittance of hepatitis B virus and other infective agents. Finally, about one tenth of the patients with severe hemophilia A do develop antibodies against Factor VIII and then become very difficult to treat as the injected Factor VIII is neutralized and inhibited by the antibodies.
There is a need for highly purified Factor VIII-containing preparations. The present specification describes such highly purified preparations. The invention also provides novel, defined fragments of Factor VIII which have improved properties compared to existing Factor VIII preparations in particular higher specific activity and longer half-life in blood. Clinical use of purified, biologically active fragments of Factor VIII can give certain advantages compared to presently used Factor VIII concentrates. The high degree of purification is an advantage as very little contamination proteins then are given to the patient and further, and more important, the risk for hepatitis B transmission is strongly diminished. A longer half-life is a great advatage as a prolonged action is obtained and thereby smaller amounts need to be given. Further for the hemophilia A patients who have developed or are at risk for developing antibodies against Factor VIII it is probably an advantage to give a smaller part of the Factor VIII molecule as it is likely to be less challenging for the immune system. As was reported recently (J. Gitschier et al. Nature 312, 330-337, 1984,
J. Toole et al. Nature 312, 342-347, 1984), intact Factor VIII can be made in cell culture using recombinant DNA techniques. An additional advantage with active fragments of Factor VIII is that such fragments can probably be made more easily and efficiently by the recombinant DNA cell culture techniques than the whole Factor VIII molecule as they are smaller and can therefore be regarded as especially advantageous to produce by this technique.